The threshold selections

excess value sample fitness test of peaks over threshold model of the flood series were deeply approached to provide a better frequency analysis method for flood designing in this paper. As a flood POT model example with the daily discharges measured at Dabai hydrologic station located in Caojiang River basin of Guangdong Province. The threshold selections were used by empirical mean excess function chart

and the Poisson distribution and the fitness indicators of excess values of peaks above different high level were tested. And then

a contrastive analysis was made among the flood models of optimal GPDandPearson Type III distribution. The main findings were as follows: 1) The Caojiang River flood extreme value distributions were heavy tail type; 2) The empirical mean excess function chart can be used as an important selection reference of Dabai flood threshold

but the optimal threshold determination should be investigated with multiindex ; 3) The good-fitness test indicated that the GPD model was better than Pearson Type III; 4) The parameter estimate methods have higher impact on the calculation results of flood return levels.